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Abstract:

A lens assembly includes a base frame, an image sensor, a lens barrel, a
lens and a backoff mechanism. By means of the backoff mechanism, the
image sensor is mounted at the base frame and movable between an
operative position and a non-operative backoff position. When the image
sensor is in the operative position, the lens barrel is in a first
position far frame the base frame, and the optical axis of the lens
intersects the image sensor. When the lens barrel is moved to a second
position close to the base frame, the image sensor is moved to the
non-operative backoff position, and the optical axis of the lens is not
intersected with the image sensor.

Claims:

1. A lens assembly of the type comprising a base frame, an image sensor,
a lens barrel and a lens, said lens barrel being movable to carry said
lens along an optical axis of said lens in direction from a first
position far from said base frame to a second position close to said base
frame, the lens assembly further comprising a backoff mechanism mounted
at said base frame and adapted for moving said image sensor between an
operative position and a non-operative backoff position in such a manner
that when said image sensor is in said operative position, said lens
barrel is in said first position and said optical axis of said lens
intersects said image sensor; when said image sensor is in said
non-operative backoff position, said image sensor is kept away from said
optical axis of said lens.

2. The lens assembly as claimed in claim 1, wherein said backoff
mechanism is moved by said lens barrel to move said image sensor from
said operative position to said non-operative backoff position when said
lens barrel is moved from said first position to said second position.

3. The lens assembly as claimed in claim 2, wherein said backoff
mechanism comprises a bump mounted at said lens barrel, a first shaft
arranged perpendicular to said optical axis, a first rotating member
abutted against said bump and movable by said bump to turn about said
first shaft, a second shaft arranged in parallel to said optical axis, a
second rotating member connected to said first rotating member and
movable by said first rotating member to turn abut said second shaft, at
least one guide rod arranged at said base frame perpendicular to said
optical axis, and a holder plate carrying said sensor and coupled to said
second rotating member and movable by said second rotating member along
said at least one guide rod.

4. The lens assembly as claimed in claim 3, wherein said first rotating
member of said backoff mechanism comprises a first toothed portion and a
first connection portion abutted against said bump; said second rotating
member comprises a second toothed portion meshed with said first toothed
portion and a second connection portion connected to said base frame.

5. The lens assembly as claimed in claim 4, wherein said first connection
portion of said first rotating member of said backoff mechanism comprises
an abutment face abutted against said bump, said abutment face sloping
outwardly from said first shaft toward a direction away from said base
frame when said lens barrel in said first position.

6. The lens assembly as claimed in claim 4, wherein said second
connection portion of said second rotating member of said backoff
mechanism comprises an elongated slot; said holder plate comprises a
coupling portion extending coupled to said elongated slot of said second
connection portion.

7. The lens assembly as claimed in claim 3, wherein said backoff
mechanism further comprises a spring member connected between said base
frame and said holder plate and adapted to provide a elastic restoring
force to return said image sensor back to said operative position.

8. The lens assembly as claimed in claim 1, wherein when said lens barrel
is in said second position to let said image sensor be moved to said
non-operative backoff position, said lens is kept closer to said base
frame than said image sensor.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to camera lens technology and more
particularly, to a lens assembly for camera, which uses a backoff
mechanism to move the image sensor away from the optical axis of the lens
when the lens is retracted, so that the thickness of the retracted
condition of the lens assembly can be minimized.

[0003] 2. Description of the Related Art

[0004] The lens assemblies of regular cameras commonly adopt a retractable
design. Thus, the lens barrel that holds a set of lenses can be extended
out of the camera housing when taking a picture, or received inside the
camera housing when not to take pictures. When retracting the lens
assembly, the lenses and optical components in the lens barrel are moved
straightly along the optical axis of the lenses toward the image sensor
(such as charge coupled device, or CCD) in the camera housing. After
retraction, the lenses, the optical components and the image sensor are
stacked up. Thus, the thickness of the camera housing must be greater
than the combined thickness of the stacked component parts. In
consequence, a camera of this design cannot be made thinner.

[0005] There are commercial cameras with a lens backoff design. For
example, Taiwan Patent 1341926 discloses a design to move one lens set to
a position at one side of the image sensor when the lens assembly is
retracted, thereby shortening the thickness of the retracted condition of
the lens assembly. Thus, the thickness of the housing of the camera using
the lens assembly can be greatly reduced. However, as the lens sets must
be moved axially and radially during retraction of the lens assembly, the
structure of the lens assembly is complicated, not convenient to
fabricate or to assemble. Therefore, an improvement in this regard is
necessary.

SUMMARY OF THE INVENTION

[0006] The present invention has been accomplished under the circumstances
in view. It is the main object of the present invention to provide a lens
assembly, which enables the camera to reduce the thickness. It is another
object of the present invention to provide a lens assembly, which has a
simple structure and is easy to make and to assemble.

[0007] To achieve this and other objects of the present invention, a lens
assembly comprises a base frame, an image sensor, a lens barrel and a
lens. The lens barrel is movable to carry the lens along an optical axis
of the lens in direction from a first position far from the base frame to
a second position close to the base frame. The lens assembly further
comprises a backoff mechanism mounted at the base frame and adapted for
moving the image sensor between an operative position and a non-operative
backoff position. When the image sensor is in the operative position, the
lens barrel is in the first position and the optical axis of the lens
intersects the image sensor. When the image sensor is in the
non-operative backoff position, the image sensor is kept away from the
optical axis of the lens.

[0008] The lens assembly is mounted inside the camera housing by means of
the base frame. When retracting the lens assembly, the lens barrel is
moved from the first position to the second position, and at the same
time, the image sensor is moved to the non-operative backoff position.
Thus, the lens can be carried by the lens barrel to the operative
position of the image sensor or over the operative position of the image
sensor to a position relatively closer to the base frame when the lens
assembly is retracted. Thus, the thickness of the lens assembly can be
greatly reduced when it is retracted. Thus, a camera using this design of
lens assembly has a low profile characteristic. Further, because the lens
and the image sensor are movable straightly back and forth, the lens
assembly has a simple structure, facilitating fabrication and assembly.

[0009] Other advantages and features of the present invention will be
fully understood by reference to the following specification in
conjunction with the accompanying drawings, in which like reference signs
denote like components of structure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is an oblique elevational view of a lens assembly for camera
in accordance with a first embodiment of the present invention,
illustrating an image sensor in an operative position.

[0016]FIG. 7 is a schematic sectional view of a lens assembly for camera
in accordance with a second embodiment of the present invention when
initiated.

[0017]FIG. 8 is a sectional view of the second embodiment of the present
invention, illustrating the lens shut-off status.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Referring to FIGS. 1-3, a lens assembly 10 in accordance with a
first embodiment of the present invention is shown comprising a base
frame 20, an image sensor 30, a lens barrel 40, a lens 50 and a backoff
mechanism 60.

[0019] The base frame 20 is adapted for mounting in a camera housing (not
shown). The image sensor 30 is mounted at the base frame 20 by means of
the backoff mechanism 60. The lens 50 is mounted in the lens barrel 40.
The lens barrel 40 is moved to a first position P1 far from the base
frame 20 (see FIGS. 1-3) when the camera initiates the lens assembly 10.
When the camera shuts off the lens assembly 10, the lens barrel 40 is
moved from the first position P1 to a second position P2 close to the
base frame 20 (see FIGS. 4-6), carrying the lens 50 along an optical axis
52 toward the base frame 20.

[0020] The lens barrel 40 may be designed to hold more lenses, lens
fixtures and other optical components. Further, as the arrangement and
movement of the lens barrel 40 are of the known art, no further detailed
description in this regard is necessary. The additional component parts
are not illustrated in the drawings, facilitating explanation of the
technical features of the present invention.

[0021] The main feature of the present invention is that, by means of the
backoff mechanism 60, the image sensor 30 is mounted at the base frame 20
and movable between an operative position P3 and a non-operative backoff
position P4. As shown in FIGS. 1-3, when the image sensor 30 is in the
operative position P3, the lens barrel 40 is in the first position P1,
and the optical axis 52 of the lens 50 is intersected with the image
sensor 30. As shown in FIGS. 4-6, when the image sensor 30 is in the
non-operative position P4, the lens barrel 40 is in the second position
P2, and the image sensor 50 is kept away from the optical axis 52 of the
lens 50.

[0022] In this embodiment, the backoff mechanism 60 comprises a bump 61, a
first shaft 62, a first rotating member 63, a second shaft 64, a second
rotating member 65, two guide rods 66, a holder plate 67, and two spring
members 68.

[0023] The bump 61 is fixedly located on the inside wall of the lens
barrel 40. Further, the bump 61 can be formed integral with the lens
barrel 40. The first shaft 62 is fixedly mounted at the base frame 20 in
a perpendicular manner relative to the optical axis 52. The first
rotating member 63 is rotatably mounted on the first shaft 62. The second
shaft 64 is fixedly located on the base frame 20 in a parallel manner
relative to the optical axis 52. The second rotating member 65 is
rotatably mounted on the second shaft 64. The two guide rods 66 are
fixedly mounted at the base frame 20 in a parallel manner relative to the
optical axis 52. The holder plate 67 is slidably mounted on the two guide
rods 66. The image sensor 30 is fixedly located on the holder plate 67.
The two spring members 68 are tensile springs connected between the base
frame 20 and the holder plate 67.

[0024] It is to be noted that, the aforesaid first shaft 62 and guide rods
66 are arranged perpendicular to the optical axis 52 without intersecting
the optical axis 52, however the aforesaid first shaft 62 and guide rods
66 can be moved to cut through the optical axis 52 at 90-degrees angle.

[0025] The first rotating member 63 comprises a first toothed portion 632
shaped like a bevel gear, and a first connection portion 634 shaped like
a triangular prism. The first connection portion 634 has an abutment face
636 facing toward the bump 61. When the lens barrel 40 is in the first
position P1, the abutment face 636 slopes outwardly from the first shaft
62 toward a direction away from the base frame 20.

[0026] The second rotating member 65 comprises a second toothed portion
652 shaped like a bevel gear and meshed with the first toothed portion
632, and a second connection portion 654 shaped like an elongated plate.
The second connection portion 654 has an elongated slot 656. The holder
plate 67 has a coupling portion 672 extends through the elongated slot
656 toward the base frame 20 (see FIG. 3).

[0027] When the lens barrel 40 is moved from the first position P1 to the
second position P2, the bump 61 is forced to push the first connection
portion 634 of the first rotating member 63 toward the base frame 20,
thereby turning the first rotating member 63 about the first shaft 62 and
simultaneously moving the second rotating member 65 to turn about the
second shaft 64 and to further forcing the holder plate 67 to move along
the guide rods 66, and therefore the image sensor 30 is moved from the
operative position P3 to the non-operative backoff position P4. When the
lens barrel 40 is moved from the second position P2 to the first position
P1, the bump 61 is no longer push the first connection portion 634 toward
the base frame 20. The two spring members 68 provide a elastic restoring
force to push the holder plate 67 and return said image sensor back to
said operative position P3.

[0028] It is to be noted that the function of the backoff mechanism 60 for
moving the image sensor 30 back to the operative position P3 is not
limited to the use of the two spring members 68. Other means for enabling
the holder plate 67 and the first rotating member 63 or second rotating
member 65 to move or to rotate reversely can be used as substitutes. For
example, torsion spring may be used and attached to the first rotating
member 63 or second rotating member 65.

[0029] Further, when retracting the lens assembly 10, the image sensor 30
is moved to the non-operative backoff position P4. Thus, the lens 50 can
be moved to the operative position P3 of the image sensor 30 or over the
operative position P3 of the image sensor 3 to a position more closer to
the base frame 20 (see FIG. 6). Thus, the lens barrel 40 can be received
deeply inside the camera housing when the lens assembly 10 is retracted,
shortening the thickness of the retracted condition of the lens assembly
10. Thus, a camera using this design of lens assembly 10 has a low
profile characteristic. Further, because the lens assembly 10 has a
simple structure, it is easy to fabricate and assemble.

[0030] FIGS. 7 and 8 illustrate a lens assembly 70 in accordance with a
second embodiment of the present invention to explain the image sensor 30
movement by means of the backoff mechanism 60.

[0031] In the lens assembly 70 of this second embodiment, a rotating
barrel 74 is mounted on the base frame, referenced by 71, to move two
lens barrels 75 and 76 toward or away from the base frame 71. Further,
each lens barrel 75 or 76 holds a respective lens set 77 or 78. The bump
61 of the backoff mechanism 60 in this second embodiment is connected to
the bottom side of the lens barrel 76. When the camera shuts off the lens
assembly 70, the lens barrel 76 is moved from the first position P1 shown
in FIG. 7 to a second position P2 shown in FIG. 8, and at the same time,
the image sensor 30 is moved away from the operative position P3 by the
backoff mechanism 60. Thus, one lens 782 of the lens set 78 is moved to
the operative position P3 of the image sensor 30, reducing the thickness
of the retracted condition of the lens assembly 70.

[0032] Although particular embodiments of the invention have been
described in detail for purposes of illustration, various modifications
and enhancements may be made without departing from the spirit and scope
of the invention. Accordingly, the invention is not to be limited except
as by the appended claims.